Extraversion/Introversion is the first distinction of the Myers Briggs Type Indicator. I find it remarkable that exactly the people who get incensed at the MBTI "because everything is shades of gray and you can't sort people into neat 16 bins", are those who are at the very very end of at least two of the four scales.
> don't let over people tell you how to think and behave!
Ironic, isn't it?